Photovoltaic devices

1. A photovoltaic device, comprising:

a window layer;

a semiconductor layer comprising a semiconductor material disposed on the window layer, wherein the semiconductor layer comprises a first region and a second region, the first region disposed in a layer proximate to the window layer, and the second region comprising a chalcogen-rich region disposed in a layer proximate to the first region,

wherein the first region and the second region comprise a dopant, and an average atomic concentration of the dopant in the second region is greater than an average atomic concentration of the dopant in the first region.

2. The photovoltaic device of claim 1 , wherein the dopant in the first region comprises copper, silver, gold, or combinations thereof.

3. The photovoltaic device of claim 1 , wherein a concentration of the dopant in the first region is substantially constant across the thickness of the first region.

4. The photovoltaic device of claim 1 , wherein the second region comprises a tellurium-rich region.

5. The photovoltaic device of claim 4 , wherein an atomic ratio of tellurium to cadmium in the tellurium-rich region is greater than about 2.

6. The photovoltaic device of claim 4 , wherein an atomic ratio of tellurium to cadmium in the tellurium-rich region is greater than about 10.

7. The photovoltaic device of claim 4 , wherein the second region further comprises a copper dopant.

8. The photovoltaic device of claim 1 , wherein the chalcogen-rich region has a thickness in a range from about 10 nanometers to about 1000 nanometers.

9. The photovoltaic device of claim 1 , wherein the dopant in the second region comprises copper, silver, gold, or combinations thereof.

10. The photovoltaic device of claim 1 , wherein an average atomic concentration of the dopant in the second region is greater than about 5×10 18 atoms/cm 3 .

11. The photovoltaic device of claim 1 , wherein a ratio of the average atomic concentration of the dopant in the second region to the average atomic concentration of the dopant in the first region is greater than about 10.

12. The photovoltaic device of claim 1 , wherein the semiconductor material comprises cadmium telluride, magnesium telluride, mercury telluride, lead telluride, zinc telluride, cadmium selenide, mercury selenide, lead selenide, zinc selenide, cadmium sulfide, mercury sulfide, zinc sulfide, lead sulfide, cadmium zinc telluride, cadmium sulfur telluride, cadmium manganese telluride, cadmium magnesium telluride, or combinations thereof.

13. The photovoltaic device of claim 1 , further comprising:

a support;

a transparent conductive layer disposed on the support; and

the window layer is disposed on the transparent conductive layer.

14. The photovoltaic device of claim 13 , further comprising a back contact layer, wherein the semiconductor layer is interposed between the window layer and the back contact layer, and wherein the second region is disposed proximate to the back contact layer.

15. The photovoltaic device of claim 1 , further comprising:

a support;

a back contact layer on the support; and

the semiconductor layer is interposed between the back contact layer and the window layer, wherein the second region is disposed proximate to the back contact layer.

16. A photovoltaic module comprising the photovoltaic device of claim 1 .

17. The photovoltaic device of claim 1 , wherein the semiconductor layer has a plurality of grain boundaries, wherein a morphology of the plurality of grain boundaries is substantially the same through the semiconductor layer.

18. A photovoltaic device, comprising:

a window layer; and

a semiconductor layer disposed on the window layer, wherein the semiconductor layer comprises a first region and a second region, the first region disposed in a layer proximate to the window layer, and the second region disposed in a layer proximate to the first region, wherein

the first region comprises a copper dopant,

the second region comprises a tellurium-rich region and a copper dopant, and

wherein an average atomic concentration of copper in the second region is greater than an average atomic concentration of the copper in the first region.

19. The photovoltaic device of claim 18 , wherein an average atomic concentration of copper in the first region is in a range from about 10 16 atoms/cm 3 to about 5×10 17 atoms/cm 3 .

20. The photovoltaic device of claim 18 , wherein an atomic concentration of copper in the first region is substantially constant across the thickness of the first region.

21. The photovoltaic device of claim 18 , wherein an atomic ratio of tellurium to cadmium in the tellurium-rich region is greater than about 2.

22. The photovoltaic device of claim 18 , wherein the tellurium-rich region has a thickness in a range from about 10 nanometers to about 1000 nanometers.

23. The photovoltaic device of claim 18 , wherein a ratio of the average atomic concentration of copper in the second region to the average atomic concentration of copper in the first region is greater than about 10.

24. The photovoltaic device of claim 18 , wherein the semiconductor layer further comprises iodine, and a concentration of iodine in the semiconductor layer varies across the thickness of the semiconductor layer.

25. The photovoltaic device of claim 18 , wherein the semiconductor material comprises cadmium telluride, magnesium telluride, mercury telluride, lead telluride, zinc telluride, cadmium selenide, mercury selenide, lead selenide, zinc selenide, cadmium sulfide, mercury sulfide, zinc sulfide, lead sulfide, cadmium zinc telluride, cadmium sulfur telluride, cadmium manganese telluride, cadmium magnesium telluride, or combinations thereof.